Virus binding to a plasma membrane receptor triggers interleukin-1 alpha-mediated proinflammatory macrophage response in vivo

Biodistribution and retargeting of FX-binding ablated adenovirus serotype 5 vectors

A major limitation for adenoviral transduction in vivo is the profound liver tropism of adenovirus type 5 (Ad5). Recently, we demonstrated that coagulation factor X (FX) binds to Ad5-hexon protein at high affinity to mediate hepatocyte transduction after intravascular delivery. We developed novel genetically FX-binding ablated Ad5 vectors with lower liver transduction. Here, we demonstrate that FX-binding ablated Ad5 predominantly localize to the liver and spleen 1 hour after injection; however, they had highly reduced liver transduction in both control and macrophage-depleted mice compared with Ad5. At high doses in macrophage-depleted mice, FX-binding ablated vectors transduced the spleen more efficiently than Ad5. Immunohistochemical studies demonstrated transgene colocalization with CD11c(+), ER-TR7(+), and MAdCAM-1(+) cells in the splenic marginal zone. Systemic inflammatory profiles were broadly similar between FX-binding ablated Ad5 and Ad5 at low and intermediate doses, although higher levels of several inflammatory proteins were observed at the highest dose of FX-binding ablated Ad5. Subsequently, we generated a FX-binding ablated virus containing a high affinity Ad35 fiber that mediated a significant improvement in lung/liver ratio in macrophage-depleted CD46(+) mice compared with controls. Therefore, this study documents the biodistribution and reports the retargeting capacity of FX binding-ablated Ad5 vectors in vitro and in vivo.

Recognition of virus infection and innate host responses to viral gene therapy vectors

The innate immune and inflammatory response represents one of the key stumbling blocks limiting the efficacy of viral-based therapies. Numerous human diseases could be corrected or ameliorated if viruses were harnessed to safely and effectively deliver therapeutic genes to diseased cells and tissues in vivo. Recent studies have shown that host cells recognize viruses using an elaborate network of sensor proteins localized at the plasma membrane, in endosomes, or in the cytosol. Three classes of sensors have been implicated in sensing viruses in mammalian cells-Toll-like receptors (TLRs), retinoid acid-inducible gene (RIG)-I-like receptors (RLRs), and nucleotide oligomerization domain (NOD)-like receptors (NLRs). The interaction of virus-associated nucleic acids with these sensor molecules triggers a signaling cascade that activates the principal host defense program aimed to limit or eliminate virus infection and restore tissue homeostasis. In addition, recent data strongly suggest that host cells can mount innate immune responses to viruses without prior recognition of their nucleic acids. To deliver therapeutic genes into the nuclei of diseased cells, viral gene therapy vectors must be efficient at penetrating either the plasma or endosomal membrane. The therapeutic use of high numbers of virus particles disturbs cellular homeostasis, triggering cell damage and stress pathways, or "sensing of modified self". Accumulating data indicate that the sensing of modified self might represent a powerful framework explaining the innate immune response activation by viral gene therapy vectors.

Viral capsid is a pathogen-associated molecular pattern in adenovirus keratitis

Human adenovirus (HAdV) infection of the human eye, in particular serotypes 8, 19 and 37, induces the formation of corneal subepithelial leukocytic infiltrates. Using a unique mouse model of adenovirus keratitis, we studied the role of various virus-associated molecular patterns in subsequent innate immune responses of resident corneal cells to HAdV-37 infection. We found that neither viral DNA, viral gene expression, or viral replication was necessary for the development of keratitis. In contrast, empty viral capsid induced keratitis and a chemokine profile similar to intact virus. Transfected viral DNA did not induce leukocyte infiltration despite CCL2 expression similar to levels in virus infected corneas. Mice without toll-like receptor 9 (Tlr9) signaling developed clinical keratitis upon HAdV-37 infection similar to wild type mice, although the absolute numbers of activated monocytes in the cornea were less in Tlr9^−/− mice. Virus induced leukocytic infiltrates and chemokine expression in mouse cornea could be blocked by treatment with a peptide containing arginine glycine aspartic acid (RGD). These results demonstrate that adenovirus infection of the cornea induces chemokine expression and subsequent infiltration by leukocytes principally through RGD contact between viral capsid and the host cell, possibly through direct interaction between the viral capsid penton base and host cell integrins.

Adenoviruses are nonenveloped DNA viruses that infect mucosal tissues, causing a wide array of diseases. Adenovirus infection of the cornea induces inflammation in the form of multifocal leukocytic infiltrates. Although studied extensively in tissue culture models, how adenoviruses induce inflammation in the living host is not well characterized in the cornea or elsewhere. Using a unique mouse model, we studied the role of viral components in the cornea, to determine which viral part(s) induce an innate immune response. We found that neither viral DNA or viral gene expression was necessary for the development of inflammation. In contrast, viral capsid, the protein coat of the virus, induced inflammation similar to intact virus. Mice lacking the toll-like receptor 9 (Tlr9) molecule, which acts as a pathogen DNA-sensing molecule within the cell, developed clinical inflammation upon adenovirus infection similar to wild type mice. Virus associated inflammation in the mouse cornea could be blocked by treatment with a peptide containing components of the adenoviral capsid. Adenovirus infection of the cornea induces inflammation principally through contact between the viral capsid and the host cell. Our study provides new insights into how the innate immune system in the eye responds to a clinically important viral pathogen.

Crystallization and preliminary X-ray diffraction analysis of human adenovirus

Replication-defective and conditionally replicating adenovirus (AdV) vectors are currently being utilized in approximately 25% of human gene transfer clinical trials. Unfortunately, progress in vector development has been hindered by a lack of accurate structural information. Here we describe the crystallization and preliminary X-ray diffraction analysis of a HAdV5 vector that displays a short flexible fiber derived from HAdV35. Crystals of Ad35F were grown in 100mM HEPES pH 7.0, 200mM Ca(OAc)(2), 14% PEG 550 MME, 15% glycerol in 100mM Tris-HCl 8.5. Freshly grown crystals diffracted well to 4.5A resolution and weakly to 3.5A at synchrotron sources. HAdV crystals belong to space group P1 with unit cell parameters a=854.03A, b=855.17A, c=865.24A, alpha=119.57 degrees , beta=91.71 degrees , gamma=118.08 degrees with a single particle in the unit cell. Self-rotation and locked-rotation function analysis allowed the determination of the particle orientation. Molecular replacement, density modification and phase-extension procedures are being employed for structure determination.

Monogenic IL-1 mediated autoinflammatory and immunodeficiency syndromes: finding the right balance in response to danger signals

INTRODUCTION

Interleukin-1 was the first cytokine identified and is a powerful inducer of fever and inflammation. The biologically active receptor for IL-1, shares signaling pathways with some pathogen recognition receptors, the Toll-like receptors (TLRs) which early on suggested an important role in innate immune function.

DISCUSSION

The discovery that some intracellular "danger receptors", the NOD like receptors (NLRs) can assemble to form multimolecular platforms, the inflammasomes, that not only sense intracellular danger but also activate IL-1beta, has provided the molecular basis for the integration of IL-1 as an early response mediator in danger recognition. The critical role of balancing IL-1 production and signaling in human disease has recently been demonstrated in rare human monogenic diseases with mutations that affect the meticulous control of IL-1 production, release and signaling by leading to decreased or increased TLR/IL-1 signaling. In diseases of decreased TLR/IL-1 signaling (IRAK-4 and MyD88 deficiencies) patients are at risk for infections with gram positive organisms; and in diseases of increased signaling, patients develop systemic autoinflammatory diseases (cryopyrin-associated periodic syndromes (CAPS), and deficiency of the IL-1 receptor antagonist (DIRA)).

CONCLUSION

Monogenic defects in a number of rare diseases that affect the balance of TLR/IL-1 signaling have provided us with opportunities to study the systemic effects of IL-1 in human diseases. The molecular defects in CAPS and DIRA provided a therapeutic rationale for targeting IL-1 and the impressive clinical results from IL-1 blocking therapies have undoubtedly confirmed the pivotal role of IL-1 in human disease and spurred the exploration of modifying IL-1 signaling in a number of genetically complex common human diseases.

Inflammasome-associated nucleotide-binding domain, leucine-rich repeat proteins and inflammatory diseases

The nucleotide-binding domain, leucine-rich repeat (NLR) proteins are a recently discovered family of intracellular pathogen and danger signal sensors. NLRs have emerged as important contributors to innate immunity in animals. The physiological impact of these genes is increasingly evident, underscored by the genetic association of variant family members with an array of inflammatory diseases. The association of mutations in NLR genes with autoinflammatory diseases indicates an important function of these genes in inflammation in vivo. This review summarizes the role of the inflammasome NLR proteins in innate immunity and inflammatory diseases and explores the possible utility of some of these NLRs as pharmacological targets.

Virus infection recognition and early innate responses to non-enveloped viral vectors

Numerous human genetic and acquired diseases could be corrected or ameliorated if viruses are harnessed to safely and effectively deliver therapeutic genes to diseased cells and tissues in vivo. Innate immune and inflammatory response represents one of the key stumbling blocks during the development of viral-based therapies. In this review, current data on the early innate immune responses to viruses and to the most commonly used gene therapy vectors (using adenovirus and adeno-associated virus) will be discussed. Recent findings in the field may help develop new approaches to moderate these innate immune anti-viral responses and thus improve the safety of viral vectors for human gene therapy applications.

Respiratory viral infections in infants: causes, clinical symptoms, virology, and immunology

In global terms, respiratory viral infection is a major cause of morbidity and mortality. Infancy, in particular, is a time of increased disease susceptibility and severity. Early-life viral infection causes acute illness and can be associated with the development of wheezing and asthma in later life. The most commonly detected viruses are respiratory syncytial virus (RSV), rhinovirus (RV), and influenza virus. In this review we explore the complete picture from epidemiology and virology to clinical impact and immunology. Three striking aspects emerge. The first is the degree of similarity: although the infecting viruses are all different, the clinical outcome, viral evasion strategies, immune response, and long-term sequelae share many common features. The second is the interplay between the infant immune system and viral infection: the immaturity of the infant immune system alters the outcome of viral infection, but at the same time, viral infection shapes the development of the infant immune system and its future responses. Finally, both the virus and the immune response contribute to damage to the lungs and subsequent disease, and therefore, any prevention or treatment needs to address both of these factors.

Current issues and future directions of oncolytic adenoviruses

Oncolytic adenoviruses (Ads) constitute a promising new class of anticancer agent. They are based on the well-studied adenoviral vector system, which lends itself to concept-driven design to generate oncolytic variants. The first oncolytic Ad was approved as a drug in China in 2005, although clinical efficacy observed in human trials has failed to reach the high expectations that were based on studies in animal models. Current obstacles to the full realization of efficacy of this class of anticancer agent include (i) limited efficiency of infection and specific replication in tumor cells, (ii) limited vector spread within the tumor, (iii) imperfect animal models and methods of in vivo imaging, and (iv) an incomplete understanding of the interaction of these agents with the host. In this review, we discuss recent advances in the field of oncolytic Ads and potential ways to overcome current obstacles to their clinical application and efficacy.

beta-Arrestins modulate Adenovirus-vector-induced innate immune responses: differential regulation by beta-arrestin-1 and beta-arrestin-2

Adenovirus (Ad)-based vectors have been utilized in human gene transfer clinical trials since 1993. Unfortunately, innate immune responses directed against the Ad capsid and/or its genetic cargo can significantly limit the usage of Ad vectors. Previous studies have demonstrated that several signaling pathways are triggered by Ads, inclusive of TLR-dependent pathways. The G-protein-coupled receptor adaptors beta-arrestin-1 (beta-Arr1) and beta-arrestin-2 (beta-Arr2) are known to have pivotal roles in regulating TLR4 triggered signaling and inflammatory responses. In this study, we examined the role of beta-arrestins in Ad5-vector-induced inflammatory responses. Our studies reveal that both beta-arrestins are capable of modulating Ad5-vector-induced inflammatory responses in vivo and in vitro. Importantly, our studies divulge another level of complexity to these responses, as our results demonstrate beta-Arr1 to be a positive regulator, and beta-Arr2 a negative regulator of Ad5 induced innate immune responses. These data may allow gene therapy biologists to more accurately study the mechanisms underlying Ad5-vector-induced immune responses, and may also direct future efforts to modulate these mechanisms to improve the safety and/or efficacy of this important gene transfer vector.

Integr-ating IL-1 alpha in antiviral host defenses

Adenoviral vectors used in gene therapy induce inflammation, although the underlying mechanisms are currently unknown. In this issue of Immunity, Di Paolo et al. (2009) implicate interleukin-1 alpha (IL- 1 alpha) in virus-induced inflammation and identify the beta 3 integrin as the key receptor regulating IL-1 alpha activity.